Auckland Transport spokeswoman Sharon Hunter admitted the platform was built for freight trains and did not suit the needs of passengers getting on and off.
"It's what we've had to put up with. We've bought trains that don't match the platform width, we have an inconsistency in that respect," she said.
The first three trains that would fit the platforms were not due to arrive until the end of next year and the roll out would not be complete until 2016.
Car dealer Graeme MacDonald was taking photos nearby when he heard sirens.
"There was blood everywhere. His partner was squatting on the ground, obviously in a seriously distressed state. I think the worst thing was that she watched it all happen. I can't imagine what she was going through."
Robson's wife Ally has been given counselling.
Robson was taken to his family marae at Oromahoe where dozens of family members gathered. His funeral was expected to take place today.
Robson's aunt, Nanette Apiata, said her nephew was a fun-loving guy who was always there for his family, especially his wife and two daughters.
"He had a big heart. He was an awesome dad, a loving dad and partner."
A group of around 30 primary school children were walking on to the platform before the adults saw what was happening and tried to turn them back, MacDonald said.
"It's a busy platform, there were a lot of students around. Everyone was standing and watching in shock."
One woman, who did not want to be named, said she was crossing the tracks nearby when she heard the "bloodcurdling scream". She rushed to Robson's side as others on the platform stood, paralysed in horror.
"I knelt by him, telling him he was going to be all right," she told the Herald on Sunday.
She sat with him for 11 minutes until the ambulance arrived. She said Robson was making sounds she hoped never to hear again.
CCTV footage captured the accident and was expected to form part of the police investigation.
Regular commuter Lucy Tawhai said she had always felt nervous stepping over the gap on the platform at Ranui.
"You have to make a concentrated effort to get over it. I've seen a lot of elderly people struggle," she said.
Henderson-Massey Local Board member Brenda Brady said she had heard the man was running for the train and slipped.
"I have been told by a number of elderly and disabled people that the gap is hard for them but they usually get help from the conductor who can bring out a ramp for them."
Veolia Transport held a blessing before the track re-opened at 6.10pm.
Pre-arranged track maintenance meant trains were not running on the western line over Easter.
Three years ago, an elderly man was dragged to his death by a train in Newmarket after his foot became trapped as he tried to get off a train.
